Audio Subsystem with Class-D Speaker
and Capless Headphone Driver
SSM2804
Rev. 0
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FEATURES
3 single-ended stereo audio inputs with optional
differential mode
Stereo, 1.4 W, filterless Class-D amplifiers with Σ-Δ modulation
Integrated receiver path bypass switch
Configurable, high performance capless headphone output
with true ground Class-G technology
Optional hardware-based headphone level limiter
I
2
C control interface
Volume control
Flexible input/output mixing
Output mode control
EMI emissions control
Automatic level control (ALC)
Adjustable headphone level limiter
Low shutdown current
Short-circuit and thermal protection
Pop-and-click suppression
Available in a 30-ball, 2.5 mm × 3.0 mm WLCSP
APPLICATIONS
Mobile phones
Portable multimedia devices
GENERAL DESCRIPTION
The SSM2804 is an audio subsystem designed specifically for
mobile phones and portable multimedia devices. This highly
flexible subsystem includes three input channels that can be
configured as single-ended stereo or monaural differential for
multimedia audio sources.
Each set of inputs is independently adjustable with the 2-wire
I
2
C interface and features an adjustable gain over a 30 dB range
in steps of 1 dB. Each set of input channels also offers the choice
of variable input impedance PGA mode or fixed input impedance
boost mode. The input signals are then mixed and routed to the
desired set of outputs. This configuration is set using the 2-wire
I
2
C control interface.
The SSM2804 includes three selectable output modes.
The first output mode is a stereo Class-D speaker driver capable
of delivering 2 × 1.4 W of continuous power to an 8 Ω bridge-tied
load (BTL) with 1% THD + N when using a 5 V supply. This
Class-D amplifier incorporates three-level Σ-Δ output modulation
designed to increase battery life and improve EMI performance.
The Class-D amplifier offers an I
2
C-adjustable volume control
with a gain range from +12 dB to −63 dB in 31 steps.
The second output mode is a pair of high performance head-
phone drivers capable of delivering 20 mW per channel into
stereo 32 Ω single-ended loads with 1% THD + N. The stereo
headphone drivers use a highly efficient, true ground centered
Class-G architecture. The headphone outputs incorporate
I
2
C-adjustable volume control with a gain range from 0 dB
to −75 dB in 32 steps.
The third output mode is an integrated receiver path bypass
switch for passing voice signals from the audio baseband.
The SSM2804 is specified over the industrial temperature range
of −40°C to +85°C. It has built-in thermal shutdown and output
short-circuit protection. The SSM2804 is available in a 30-ball,
2.5 mm × 3.0 mm wafer level chip scale package (WLCSP).
